This is a study of the post-operative rehabilitation of flexor tendon injuries in the hand, which are common injuries. The repair of lacerated flexor tendons continues to be a major unsolved problem in hand surgery. The current concept of early post-operative motion has proven to be effective in experimental investigations and seems to offer the best promise of improved results in terms of function of the hand, decreased time lost from work, and decreased disability compensation. The published work to date has shown the effectiveness of early passive motion both histologically in dogs mobilized for five minutes per day and clinically in patients mobilized for various short periods of time per day. No study to date has shown the effects of prolonged periods of motion. This project proposes to study the histological, ultrastructural, and mechanical effects of prolonged passive motion on healing flexor tendons in an established animal model. Leghorn chickens will have an experimentally-induced flexor tendon laceration in the foot. The animals will be divided into immobilized and mobilized groups. The immobilized animals will be placed in casts. The mobilized animals will have intermittent passive motion provided by a mounted, battery-operated device that has been developed at CWRU. The animals will be sacrificed at intervals up to one month. Tendon specimens will be examined: (1) histologically for origins of reparative tissues and occurence of adhesions; (2) mechanically for tendon strength, gliding function, and range of motion; (3) ultrastructurally for collagen synthesis, degradation and reorientation. The long-term goal is to understand the effects of intermittent passive motion on healing flexor tendons and to design a protocol for the post-operative treatment of flexor tendon injuries. This should improve the results from tendon surgery, decrease patient disability, and decrease the amount of rehabilitation time before the patient can return to work.